body,html{
    width: 100%;
    height: 100%;
    max-width: 600px;
    padding:0;
    margin: 0;
    overflow: hidden;
    /* // 过渡动画 */
}
img{
    width: 50%;
    height: auto;
}

body{
    box-sizing: border-box;
}
.content{
    padding: 10px;
    transition: background-color ;
}
div.pic img{
    width: 100%;
}
#modeCheckBox{
    display: none;
}
#introduction{
    
    width: 50%;
    height: auto;
}
header{
    display: flex;
    justify-content: space-between;
    
    width: 50%;
    height: auto;
}
/* version 2  */
body.night{
    color: white;
    background-color: black;
    transition: all 1s; /* // 过渡动画 */
}